As one of 300 million owners of the continent, in proper AMERICAN, I had said that the motor mount on the passenger side was LOADED under torque ( conditions ). Thus in compression its motion would be limited where as the driver side can raise (rear up ) several inches in a most threatening manner. LONG time ago I had strapped down the driver side with a SS cable to reduce the stress-load on the driver side.

The clunk is most likely play in the drive train, and left untreated may lead to failure of big pieces. 2 years ago on the way to carlisle I passed a vehicle full power at a century and the rear ring ate my pinion in a hostile manner. Clunks are bad. Woody